• In the late 1890's he used the cathode ray gun to identify the first subatomic particle - the electron
• "Chocolate chip cookie" or "plum pudding" model - negatively charged electrons are distributed throughout a uniform positive charge 

• In 1911 he performed the "gold foil experiment" with radioactive particles to prove the existence of the nucleus
• He established that the nucleus was small, dense, and positively charged. Assumed that electrons were outside the nucleus. 

• He proposed a "new" atomic structure, placing electrons in specific paths around the nucleus, using the solar system as a model
• This model only works for simple atoms 

• Electrons do not move about the atom's nucleus in a definite path like planets around the Sun
• A probable location of an electron can be determined based on its energy
• Energy levels are divided into 5 sublevels called orbitals
• Electrons move randomly in electron clouds called orbitals

• Greek Philosopher
• 1st person to propose the idea that matter was not infinitely divisible
• He believed that matter was made up of tiny individual particles called atomos, from which the English word atom was derived.
• He believed that atomos could not be created, destroyed or further divided.
• Matter is composed of empty space through which atomos move
• Atomos are soild, homogeneous, indestructible and indivisible
• Different kinds of atomos have different sizes and shapes
• The differing properties of matter are due to the size, shape and movement of atomos
• Apparent changes in matter result from changes in groupings of atomos and not from changes in the atomos themselves. 
• His ideas were not based on science. He did not have the benefit of being able to conduct controlled experiments to test if his ideas were valid.

• Influential Greek philosopher
• Rejected the concept of the atom
• Rejected the atomic "theory" because it did not agree with his own ideas on nature. One of his major critiscims concerned the idea that atoms moved through empty space. He did not believe that the "nothingness" of empty space could exist 

• They searched for the Philosopher's Stone, which had the ability to transform base materials like copper or lead, into valuable substances, like gold.
• They also searched for the Elixir of Life, which when drunk by a particular person, would grant him immortality. 

• All matter is composed of extremely small particles called atoms
• All atoms of a given element are identical, having the same mass, size and chemical properties. Atoms of a specific element are different from those of any other element
• Atoms cannot be created, divided into smaller particles or destroyed
• Different atoms combine to form compounds
• In a chemical reaction, atoms are separated, combined or rearranged 

Who wrote an equation that treated the electron as a wave?

And afterwards created wavefunctions called "orbitals"

True and False

Gas in space emits radio waves

True or False

The photons that make up radio waves travel at the same speed as teh photons that make up visible light.

True or False

Low energy photons act like waves. High energy photons act like particles.

• Each electron occupies the lowest energy orbital
• Electrons are Lazy
• All orbits related to an energy level are of equal energy
• The three 2p orbitals are the same energy level
•  

• Single electrons with the same spin must occupy each equal-energy orbital before additional electrons with opposite spins can occupy the same orbitals
• Electrons are unfriendly
   

• A maximum of two electrons may occupy a single orbital, but if the electrons have opposite spins
• Spin - Electrons have an associated "spin," either one way or the other, like a top
• These spins are called "spin up" and "spin down" 

Is simply the distance from the nucleus to the outermost electron.

As half the distance betwen the nuclei of two bonded atoms of the smae element(covalent bond)

• As a group decrease, the outermost electron is in a higher energy level which is further from the nucleus so the radius increases.
• Across a period, electrons are being added to the same energy level, but the number of protons in the nucleus increases, this attracts the energy level closer to the nucleus and the atomic radius decreases across a period. 

• An element increases in size down a group as the number of electron shells increase.
• Across a period, the ionic radius decreases from Group 1 to Group 3